Ashok Kumar Malik

A review on development of solid phase microextraction fibers by sol–gel methods and their applications

Solid phase microextraction (SPME) is an innovative, solvent free technology that is fast, economical and versatile. SPME is a fiber coated with a liquid (polymer), a solid (sorbent) or a combination of both. The fiber coating takes up the compounds from the sample by absorption in the case of liquid coatings or adsorption in the case of solid coatings. The SPME fiber is then transferred with the help of a syringe like device into the analytical instrument for desorption and analysis of the target analytes. The sol-gel process provides a versatile method to prepare size, shape and charge selective materials of high purity and homogeneity by means of preparation techniques different from the traditional ones, for the chemical analysis. This review is on the current state of the art and future trends in the developments of solid phase microextraction (SPME) fibers using sol-gel method. To achieve more selective determination of different compound classes, the variety of different coating material for SPME fibers has increased. Further developments in SPME as a highly efficient extraction technique, will greatly depend on new breakthroughs in the area of new coating material developments for the SPME fibers. In sol-gel approach, appropriate sol-gel precursors and other building blocks can be selected to create a stationary phase with desired structural and surface properties. This approach is efficient in integrating the advantageous properties of organic and inorganic material systems and thereby increasing and improving the extraction selectivity of the produced amalgam organic-inorganic stationary phases. This review is mainly focused on recent advanced developments in the design, synthesis, characterisation, properties and application of sol-gel in preparation of coatings for the SPME fibers.

Liquid chromatography-mass spectrometry in food safety.

The use of powerful mass spectrometric detectors in combination with liquid chromatography has played a vital role to solve many problems related to food safety. Since this technique is especially well suited for, but not restricted to the analysis of food contaminants within the food safety area, this review is focused on providing an insight into this field. The basic legislation in different parts of the world is discussed with a focus on the situation within the European Union (EU) and why it favors the use of liquid chromatography-mass spectrometry (LC-MS). Main attention in this review is on the achievements that have been possible because of the latest advances and novelties in mass spectrometry and how these progresses have influenced the best control of food allowing an increase in the food safety and quality standards. Emphasis is given to the potential and pitfalls of the different LC-MS approaches as well as in its possibilities to address current hot issues in food safety, such as the development of large-scale multi-residue methods and the identification of non-target and unknown compounds. Last but not least, future perspectives and potential directions are also outlined highlighting prospects and achievements.

A review on solid phase microextraction- : High performance liquid chromatography as a novel tool for the analysis of toxic metal ions

This paper reviews the practical applications of solid phase microextraction-High performance liquid chromatography in the analysis of toxic metal species as these are important contaminants and are carcinogenic. Their determination in formulations, in feed and food, and in complex environmental matrices (e.g., waste water and industrial effluents) often requires analytical methods capable of high efficiency, unique selectivity, and high sensitivity. Solid phase microextraction (SPME) requires low solvent consumption and is quick in use. SPME is used for extraction and online desorption of analytes with the mobile phase of HPLC and subsequent detection by UV, ICP-MS or ESI-MS as detectors. Different SPME-HPLC methods are summarized in this article to demonstrate the usefulness of this technique for metallic species of As, Cr, Pb, Hg and Se.

Efficient analysis of selected estrogens using fabric phase sorptive extraction and high performance liquid chromatography-fluorescence detection.

A simple, fast and sensitive analytical method using fabric phase sorptive extraction (FPSE) followed by high performance liquid chromatography with fluorescence detection (HPLC-FLD) has been developed for efficient quantification of biologically important molecules e.g., 17α-ethynylestradiol (EE2), β-estradiol (E2) and bisphenol A (BPA). FPSE is a new sorptive extraction technique that integrates the advantages of permeable sol-gel derived hybrid organic-inorganic sorbents with flexible and permeable fabric substrates, resulting in a highly efficient and sensitive extraction media that can be introduced directly into any kind of fluidic matrix. Various factors affecting the performance of FPSE technique were optimized. The chromatographic separation was carried using mobile phase acetonitrile/methanol/water (30:15:55; v/v) at a flow rate 1.0mL/min on C18 column with fluorescence detection (λex=280nm and λem=310nm). The calibration curves of the target analytes were prepared with good correlation coefficient values (R(2)>0.992). Limit of detection (LOD) values range from 20 to 42pg/mL. The developed method was applied successfully for the analysis of estrogen molecules in urine and various kinds of aqueous samples.

Methods of analysis of dithiocarbamate pesticides: a review

This review incorporates a brief introduction to methods for the analysis of dithiocarbamate pesticides followed by a more detailed discussion of individual methods. Determination of dithiocarbamate residues from foodstuffs, water and commercial samples and in various environmental samples using different techniques is a key feature.

A new method for determination of myricetin and quercetin using solid phase microextraction–high performance liquid chromatography–ultra violet/visible system in grapes, vegetables and red wine samples

A new approach for the extraction and determination of myricetin and quercetin by using SPME-HPLC-UV system has been developed. The method involves adsorption of flavonoids on CAR/TPR fiber followed by desorption in the desorption chamber of SPME-HPLC interface using citrate buffer (0.001 M):acetonitrile (70:30) as mobile phase and UV detection at 372 nm. The detection limits for myricetin and quercetin are 48.3 and 24.7 pgmL(-1), respectively. The proposed method was validated by determining myricetin and quercetin in tomato, onion, grapes and red wine samples.

Sample preparation methods for the determination of pesticides in foods using CE-UV/MS.

Much progress has been made in pesticide analysis over the past decade, during this time hyphenated techniques involving highly efficient separation with sensitive detection have become the techniques of choice. Among these, methods based on separation with mass spectrometric detection have resulted in greater likelihood of identification and are acknowledged to be extremely useful and authoritative methods for the determination of pesticide residues but the inherent advantages of the use of CE as a separation technique are well‐known and can be summarized as high separation efficiency, low analysis time, high resolution power, and low consumption of samples and reagents. Although UV is the most widely used detector in CE equipments so far so this detection mode is also included for the review. Even with such powerful instrumental techniques, however, the risk of interference increases with the complexity of the matrix studied, so sample preparation is often the limiting step in systems before instrumental analysis and is still mandatory in many applications, for example, food analysis. This article summarizes the analytical characteristics of the different methods of sample preparation for the determination of pesticide residues in a variety of food matrices, and surveys their recent applications in combination with CE using UV and MS detectors. We will discuss the advantages and the disadvantages of different methods, the instrumental aspects, summarize and conclude the perspectives for the future.

Development of a new SPME–HPLC–UV method for the analysis of nitro explosives on reverse phase amide column and application to analysis of aqueous samples

A rapid, simple, sensitive and accurate quantitative method has been developed for the determination of eleven nitroaromatic components by solid phase microextraction (SPME) coupled to high performance liquid chromatography (HPLC) with UV detection from aqueous samples. PDMS/DVB resin fiber (60 microm) was used for concurrent extraction of all the analytes from aqueous matrix. Static desorption was carried out in the desorption chamber of SPME-HPLC interface containing mobile phase; methanol:water 43:57 (v/v) with subsequent liquid chromatographic analysis at isocratic flow rate of 1.3 mL/min and detection at 254 nm. A reverse phase amide column (5 microm) was used as a separation medium. The limit of detection (S/N=3) for TNT and Tetryl was found to be 0.35 and 0.54 ng/mL, respectively. Developed method has been applied successfully to the analysis of aqueous samples obtained from environmental and industrial sources like river water, ground water, drinking water and industrial waste water.

Amines in the Environment

The determination of the amines in the environment is very important. In this review, different methods for the analysis of the amines in the environment are discussed. Different aspects of the toxicity of the amines are discussed in detail. Methods for the sampling of the amines in air, soil, and water are discussed. Though there different techniques for the analysis of the amines only high performance liquid chromatography, gas chromatography, and capillary electrophoresis are discussed here. The different draw back, of these methods and their advantages are discussed in detail. The salient feature of the review is the discussion on the application of these methods for the determination of the amines in soil, water, and air, i.e., environmental samples.

Spectrophotometric Methods for the Determination of Fluoroquinolones: A Review

The majority of quinolones of clinical use belong to the subset of fluoroquinolones, which have a fluoro group attached the central ring system, typically at the 6-position. Fluoroquinolones are widely used in human and veterinary medicine. In recent times there has been significant development in the field of fluoroquinolones and many new analogues have been synthesized. The clinical and pharmaceutical analysis of these drugs requires effective analytical procedures for quality control and pharmacodynamic and pharmacokinetic studies. In this review article, various spectrophotometric methods used for determination of fluoroquinolones have been covered. The methods include visible spectrophotometry, which is based on formation of ion-pair or charge transfer complexes, UV spectrophotometry and derivative spectrophotometry. The application of these methods for the determination of fluoroquinolones in pharmaceutical and real samples has also been discussed.